The so-called absorbing materials refer to a class of materials that can absorb or greatly weaken the electromagnetic wave energy received by its surface, thereby reducing the interference of electromagnetic waves.
In engineering applications, they require the absorbing material to have a high absorption rate of electromagnetic waves in a wide frequency band, they also require to have light weight, temperature resistance, moisture resistance, corrosion resistance and other properties.
Three commonly used nano materials for absorbing materials are as follows:
1. Carbon series nano materials: nano graphene, carbon nanotubes, etc.
Carbon nanotubes(CNTs) show excellent absorbing properties, and at the same time have the characteristics of light weight, good compatibility, and wide absorbing frequency band. They are the most potential absorbing materials of the new generation.
2. Iron series nanomaterials: nano iron(Fe) powder, nano iron oxide, etc.
Nano metals and alloys are mainly used as wave absorbers in a multi-phase composite way, mostly Fe, Co, Ni and other nano metals and alloy powders, and their wave-absorbing properties are better than single-phase nano metal powders.
3. Ceramic series nanomaterials. Such as silicon carbide whiskers, nano silicon carbide particles, nano silicon nitride, and so on.
Silicon carbide(SiC) has been studied a lot as an absorbent. Silicon carbide not only has certain wave absorbing properties, but also can weaken the infrared signal of the engine, and has the advantages of high temperature resistance, low relative density, good toughness, high strength and high resistivity. SiC is one of the rapidly developing absorbents abroad. The absorption band of nano silicon carbide is wider, and it has a good absorption effect on the millimeter and centimeter bands.
In the increasingly important stealth and electromagnetic compatibility (EMC) technology, the role and status of electromagnetic wave absorbing materials are very prominent. So far, nano-wave absorbing materials mainly work in two aspects: civil and military.
In civilian use, nano-wave absorbing materials are mainly used in human body protection. Due to the application of high-power radar, communication machine, microwave heating and other equipment, preventing electromagnetic radiation or leakage and protecting the health of operators is a new and complex topic, and absorbing materials can achieve this purpose. In addition, today’s household appliances generally have electromagnetic radiation problems, which can also be effectively suppressed by rational use of absorbing materials and their components. .
In the military, it is mainly used in radar shadow technology. Coating absorbing materials on various weapons equipment and military facilities such as aircraft, missiles, tanks, ships, warehouses, etc. can absorb reconnaissance radio waves and attenuate reflected signals, thereby breaking through the defense area of enemy radar. This is a kind of anti-radar reconnaissance, a powerful means of reducing the exposure of weapon systems to infrared-guided missiles and laser weapons.
Nano absorbing materials have the characteristics of light weight, wide frequency bandwidth and good performance, and have a wide range of applications. In the case of the same material, nano size materials are obviously better and can meet the requirements of the development of the times for absorbing materials. It is foreseeable that nano absorbing materials will play a huge role in thermal insulation and energy saving, environmental protection, human protection, and military stealth technology in the future.